Measuring roughly 9.5 metres north to south and 8 metres east to west, it is a spread of burnt material, the characteristic residue of a fulacht fia. These are among the most common prehistoric monuments in Ireland: outdoor cooking sites, typically Bronze Age in date, where stones were heated in a fire and then dropped into a water-filled trough to bring it to the boil. The cracked and shattered stones were raked aside after each use, and it is precisely this accumulation of fire-reddened, heat-fractured material that gives a fulacht fia its distinctive low mound profile, and that makes it visible at all after three or four thousand years.

The site at Coolacoosane was noted by Bowman in 1934, who recorded two fulachta fiadh in the area, one on land then belonging to a P. Duane and the other on land belonging to a P.D. O'Connor. This particular mound is thought to be one of that pair, though which of the two landholdings it falls within is not entirely settled. The fact that it now sits in reclaimed pasture suggests the landscape around it has been altered considerably since prehistoric times, as agricultural improvement over the centuries has a way of absorbing and obscuring earthworks that were once more prominently visible.